1. Field of the Invention
Apparatuses and methods consistent with the present invention relate generally to a mold for injection molding and, more particularly, to a mold for injection molding having a plurality of curved runners, and a molding method using the same.
2. Description of the Prior Art
A mold for injection molding has a runner for guiding molten resin fed through a sprue into a mold cavity for molding a product. In this case, an exit of the runner is called a gate. In the case where the gate is located on the outer surface of a molded product, a mark of the gate remains on the outer surface of the molded product, and thus it is difficult to provide an aesthetically pleasing external appearance. As such, the mold, which is disclosed in Japanese Patent Application Publication No. Hei 10(1998)-95033, employs a curved runner capable of providing a gate to the rear surface of a molded product.
The mold disclosed in this document includes a first runner provided at a parting portion of a stationary mold and a movable mold, and a second curved runner connecting a mold cavity with the first runner. The second runner has an arcuate shape, and a cross-sectional area that is gradually reduced from an entry connected with the first runner to a gate.
This mold can prevent the mark of the gate from remaining on the outer surface (i.e., front surface) of the molded product because the gate of the second runner is located on the rear surface of the molded product. Further, when the movable mold is separated from the stationary mold, the molded product can be separated from the gate of the second runner, and a form of the resin filled in the second runner can be separated from the mold while being elastically deformed.
This mold makes it possible to mold a product having a simple shape and a small size. However, because the gate is located only at a limited position of the mold cavity, the mold can be subjected to a short run of the molten resin when a thin, wide, flat product or a tortuous product is molded. In the case of the mold employing the curved runner, it is difficult to construct multiple gates due to the difficulty in removing a form in the runner in the future.